Feedback based controller for varying content item density

ABSTRACT

Techniques for varying content item density are provided. A first minimum gap value is stored that dictates how close two content items of a first type may appear in a content item feed that contains content items of multiple types that includes the first type and a second type. The first minimum gap value is used to place content items in a first set of content item feeds. For each content item feed of the first set of content item feeds, performance data that indicates how well content items of the first type perform in the content item feed is generated. Based on the performance data and the first minimum gap value, a second minimum gap value that is different than the first minimum gap value is generated. The second minimum gap value is used to place content items in a second plurality of content item feeds.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. application Ser. No. 16/141,669,filed Sep. 25, 2018 entitled “AUTOMATICALLY MERGING MULTIPLE CONTENTITEM QUEUES”, the entire contents of which is hereby incorporated byreference as if fully set forth herein.

TECHNICAL FIELD

The present disclosure relates to network-transferred electronic contentitems and, more particularly to, a feedback controller that variesdensity of certain types of electronic content items on different clientdevices

BACKGROUND

The Internet has enabled the delivery of electronic content to billionsof people. Some content providers desire to send additional contentitems to users who visit a website hosted by a third-party publishersystem. To do so, content providers may rely on a content deliveryservice that delivers the additional content items to computing devicesof such users. In one approach, a content provider provides, to thecontent delivery service, data that indicates one or more userattributes that users must satisfy in order to receive the additionalcontent items. The content delivery service creates a content deliverycampaign that includes the data and is intended for sending additionalcontent items to computing devices of users who will visit the website.However, if too many content items of a particular type are displayed atone time, then users that are not interested in content items of thattype will begin to ignore those content items completely and will beless likely to interact with those content items.

The approaches described in this section are approaches that could bepursued, but not necessarily approaches that have been previouslyconceived or pursued. Therefore, unless otherwise indicated, it shouldnot be assumed that any of the approaches described in this sectionqualify as prior art merely by virtue of their inclusion in thissection.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a block diagram that depicts a system for distributing contentitems to one or more end-users, in an embodiment;

FIG. 2 is a flow diagram that depicts an example process for adjusting aminimum gap value for content items of a particular type, in anembodiment;

FIG. 3 is a block diagram that depicts an example workflow for updatingminimum gap values using different techniques and for differentsegments, in an embodiment;

FIG. 4 is a block diagram that illustrates a computer system upon whichan embodiment of the invention may be implemented.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however,that the present invention may be practiced without these specificdetails. In other instances, well-known structures and devices are shownin block diagram form in order to avoid unnecessarily obscuring thepresent invention.

General Overview

A system and method for modifying a frequency with which content itemsof a particular type appear in a content item feed are provided. In onetechnique, a minimum gap value is defined and used to dictate how closecontent items of the particular type may appear in web content, such asa feed. Performance of content items of the particular type is monitoredand used to determine whether to adjust the minimum gap. In onetechnique, a PID controller is implemented that adjusts the minimum gapvalue in response to changes in performance.

Embodiments described herein improve computer technology. Currentapproaches to including content items of the particular type in webcontent did not consider user “blindness” of such content items whenselecting how many content items to insert and/or how to space thecontent items in the web content. Instead, current approaches reliedsimply on relevancy or value of the content items to the host platformin determining what to display in web content. Embodiments result indecreased blindness, increased user engagement, and increased value ofthe content items. Furthermore, embodiments described herein involve anew type of information, namely a minimum gap value, and a technique formodifying this new type of information.

System Overview

FIG. 1 is a block diagram that depicts a system 100 for distributingcontent items to one or more end-users, in an embodiment. System 100includes content providers 112-116, a content delivery system 120, apublisher system 130, and client devices 142-146. Although three contentproviders are depicted, system 100 may include more or less contentproviders. Similarly, system 100 may include more than one publisher andmore or less client devices.

Content providers 112-116 interact with content delivery system 120(e.g., over a network, such as a LAN, WAN, or the Internet) to enablecontent items to be presented, through publisher system 130, toend-users operating client devices 142-146. Thus, content providers112-116 provide content items to content delivery system 120, which inturn selects content items to provide to publisher system 130 forpresentation to users of client devices 142-146. However, at the timethat content provider 112 registers with content delivery system 120,neither party may know which end-users or client devices will receivecontent items from content provider 112.

An example of a content provider includes an advertiser. An advertiserof a product or service may be the same party as the party that makes orprovides the product or service. Alternatively, an advertiser maycontract with a producer or service provider to market or advertise aproduct or service provided by the producer/service provider. Anotherexample of a content provider is an online ad network that contractswith multiple advertisers to provide content items (e.g.,advertisements) to end users, either through publishers directly orindirectly through content delivery system 120.

Although depicted in a single element, content delivery system 120 maycomprise multiple computing elements and devices, connected in a localnetwork or distributed regionally or globally across many networks, suchas the Internet. Thus, content delivery system 120 may comprise multiplecomputing elements, including file servers and database systems. Forexample, content delivery system 120 includes (1) a content providerinterface 122 that allows content providers 112-116 to create and managetheir respective content delivery campaigns and (2) a content deliveryexchange 124 that conducts content item selection events in response tocontent requests from a third-party content delivery exchange and/orfrom publisher systems, such as publisher system 130.

Publisher system 130 provides its own content to client devices 142-146in response to requests initiated by users of client devices 142-146.The content may be about any topic, such as news, sports, finance, andtraveling. Publishers may vary greatly in size and influence, such asFortune 500 companies, social network providers, and individualbloggers. A content request from a client device may be in the form of aHTTP request that includes a Uniform Resource Locator (URL) and may beissued from a web browser or a software application that is configuredto only communicate with publisher system 130 (and/or its affiliates). Acontent request may be a request that is immediately preceded by userinput (e.g., selecting a hyperlink on web page) or may be initiated aspart of a subscription, such as through a Rich Site Summary (RSS) feed.In response to a request for content from a client device, publishersystem 130 provides the requested content (e.g., a web page) to theclient device.

Simultaneously or immediately before or after the requested content issent to a client device, a content request is sent to content deliverysystem 120 (or, more specifically, to content delivery exchange 124).That request is sent (over a network, such as a LAN, WAN, or theInternet) by publisher system 130 or by the client device that requestedthe original content from publisher system 130. For example, a web pagethat the client device renders includes one or more calls (or HTTPrequests) to content delivery exchange 124 for one or more contentitems. In response, content delivery exchange 124 provides (over anetwork, such as a LAN, WAN, or the Internet) one or more particularcontent items to the client device directly or through publisher system130. In this way, the one or more particular content items may bepresented (e.g., displayed) concurrently with the content requested bythe client device from publisher system 130.

In response to receiving a content request, content delivery exchange124 initiates a content item selection event that involves selecting oneor more content items (from among multiple content items) to present tothe client device that initiated the content request. An example of acontent item selection event is an auction.

Content delivery system 120 and publisher system 130 may be owned andoperated by the same entity or party. Alternatively, content deliverysystem 120 and publisher system 130 are owned and operated by differententities or parties.

A content item may comprise an image, a video, audio, text, graphics,virtual reality, or any combination thereof. A content item may alsoinclude a link (or URL) such that, when a user selects (e.g., with afinger on a touchscreen or with a cursor of a mouse device) the contentitem, a (e.g., HTTP) request is sent over a network (e.g., the Internet)to a destination indicated by the link. In response, content of a webpage corresponding to the link may be displayed on the user's clientdevice.

Examples of client devices 142-146 include desktop computers, laptopcomputers, tablet computers, wearable devices, video game consoles, andsmartphones.

Bidders

In a related embodiment, system 100 also includes one or more bidders(not depicted). A bidder is a party that is different than a contentprovider, that interacts with content delivery exchange 124, and thatbids for space (on one or more publisher systems, such as publishersystem 130) to present content items on behalf of multiple contentproviders. Thus, a bidder is another source of content items thatcontent delivery exchange 124 may select for presentation throughpublisher system 130. Thus, a bidder acts as a content provider tocontent delivery exchange 124 or publisher system 130. Examples ofbidders include AppNexus, DoubleClick, and LinkedIn. Because bidders acton behalf of content providers (e.g., advertisers), bidders createcontent delivery campaigns and, thus, specify user targeting criteriaand, optionally, frequency cap rules, similar to a traditional contentprovider.

In a related embodiment, system 100 includes one or more bidders but nocontent providers. However, embodiments described herein are applicableto any of the above-described system arrangements.

Content Delivery Campaigns

Each content provider establishes a content delivery campaign withcontent delivery system 120 through, for example, content providerinterface 122. An example of content provider interface 122 is CampaignManager™ provided by LinkedIn. Content provider interface 122 comprisesa set of user interfaces that allow a representative of a contentprovider to create an account for the content provider, create one ormore content delivery campaigns within the account, and establish one ormore attributes of each content delivery campaign. Examples of campaignattributes are described in detail below.

A content delivery campaign includes (or is associated with) one or morecontent items. Thus, the same content item may be presented to users ofclient devices 142-146. Alternatively, a content delivery campaign maybe designed such that the same user is (or different users are)presented different content items from the same campaign. For example,the content items of a content delivery campaign may have a specificorder, such that one content item is not presented to a user beforeanother content item is presented to that user.

A content delivery campaign is an organized way to present informationto users that qualify for the campaign. Different content providers havedifferent purposes in establishing a content delivery campaign. Examplepurposes include having users view a particular video or web page, fillout a form with personal information, purchase a product or service,make a donation to a charitable organization, volunteer time at anorganization, or become aware of an enterprise or initiative, whethercommercial, charitable, or political.

A content delivery campaign has a start date/time and, optionally, adefined end date/time. For example, a content delivery campaign may beto present a set of content items from Jun. 1, 2015 to Aug. 1, 2015,regardless of the number of times the set of content items are presented(“impressions”), the number of user selections of the content items(e.g., click throughs), or the number of conversions that resulted fromthe content delivery campaign. Thus, in this example, there is adefinite (or “hard”) end date. As another example, a content deliverycampaign may have a “soft” end date, where the content delivery campaignends when the corresponding set of content items are displayed a certainnumber of times, when a certain number of users view, select, or clickon the set of content items, when a certain number of users purchase aproduct/service associated with the content delivery campaign or fillout a particular form on a website, or when a budget of the contentdelivery campaign has been exhausted.

A content delivery campaign may specify one or more targeting criteriathat are used to determine whether to present a content item of thecontent delivery campaign to one or more users. (In most contentdelivery systems, targeting criteria cannot be so granular as to targetindividual members.) Example factors include date of presentation, timeof day of presentation, characteristics of a user to which the contentitem will be presented, attributes of a computing device that willpresent the content item, identity of the publisher, etc. Examples ofcharacteristics of a user include demographic information, geographicinformation (e.g., of an employer), job title, employment status,academic degrees earned, academic institutions attended, formeremployers, current employer, number of connections in a social network,number and type of skills, number of endorsements, and stated interests.Examples of attributes of a computing device include type of device(e.g., smartphone, tablet, desktop, laptop), geographical location,operating system type and version, size of screen, etc.

For example, targeting criteria of a particular content deliverycampaign may indicate that a content item is to be presented to userswith at least one undergraduate degree, who are unemployed, who areaccessing from South America, and where the request for content items isinitiated by a smartphone of the user. If content delivery exchange 124receives, from a computing device, a request that does not satisfy thetargeting criteria, then content delivery exchange 124 ensures that anycontent items associated with the particular content delivery campaignare not sent to the computing device.

Thus, content delivery exchange 124 is responsible for selecting acontent delivery campaign in response to a request from a remotecomputing device by comparing (1) targeting data associated with thecomputing device and/or a user of the computing device with (2)targeting criteria of one or more content delivery campaigns. Multiplecontent delivery campaigns may be identified in response to the requestas being relevant to the user of the computing device. Content deliveryexchange 124 may select a strict subset of the identified contentdelivery campaigns from which content items will be identified andpresented to the user of the computing device.

Instead of one set of targeting criteria, a single content deliverycampaign may be associated with multiple sets of targeting criteria. Forexample, one set of targeting criteria may be used during one period oftime of the content delivery campaign and another set of targetingcriteria may be used during another period of time of the campaign. Asanother example, a content delivery campaign may be associated withmultiple content items, one of which may be associated with one set oftargeting criteria and another one of which is associated with adifferent set of targeting criteria. Thus, while one content requestfrom publisher system 130 may not satisfy targeting criteria of onecontent item of a campaign, the same content request may satisfytargeting criteria of another content item of the campaign.

Different content delivery campaigns that content delivery system 120manages may have different charge models. For example, content deliverysystem 120 (or, rather, the entity that operates content delivery system120) may charge a content provider of one content delivery campaign foreach presentation of a content item from the content delivery campaign(referred to herein as cost per impression or CPM). Content deliverysystem 120 may charge a content provider of another content deliverycampaign for each time a user interacts with a content item from thecontent delivery campaign, such as selecting or clicking on the contentitem (referred to herein as cost per click or CPC). Content deliverysystem 120 may charge a content provider of another content deliverycampaign for each time a user performs a particular action, such aspurchasing a product or service, downloading a software application, orfilling out a form (referred to herein as cost per action or CPA).Content delivery system 120 may manage only campaigns that are of thesame type of charging model or may manage campaigns that are of anycombination of the three types of charging models.

A content delivery campaign may be associated with a resource budgetthat indicates how much the corresponding content provider is willing tobe charged by content delivery system 120, such as $100 or $5,200. Acontent delivery campaign may also be associated with a bid amount thatindicates how much the corresponding content provider is willing to becharged for each impression, click, or other action. For example, a CPMcampaign may bid five cents for an impression, a CPC campaign may bidfive dollars for a click, and a CPA campaign may bid five hundreddollars for a conversion (e.g., a purchase of a product or service).

Content Item Selection Events

As mentioned previously, a content item selection event is when multiplecontent items (e.g., from different content delivery campaigns) areconsidered and a subset selected for presentation on a computing devicein response to a request. Thus, each content request that contentdelivery exchange 124 receives triggers a content item selection event.

For example, in response to receiving a content request, contentdelivery exchange 124 analyzes multiple content delivery campaigns todetermine whether attributes associated with the content request (e.g.,attributes of a user that initiated the content request, attributes of acomputing device operated by the user, current date/time) satisfytargeting criteria associated with each of the analyzed content deliverycampaigns. If so, the content delivery campaign is considered acandidate content delivery campaign. One or more filtering criteria maybe applied to a set of candidate content delivery campaigns to reducethe total number of candidates.

As another example, users are assigned to content delivery campaigns (orspecific content items within campaigns) “off-line”; that is, beforecontent delivery exchange 124 receives a content request that isinitiated by the user. For example, when a content delivery campaign iscreated based on input from a content provider, one or more computingcomponents may compare the targeting criteria of the content deliverycampaign with attributes of many users to determine which users are tobe targeted by the content delivery campaign. If a user's attributessatisfy the targeting criteria of the content delivery campaign, thenthe user is assigned to a target audience of the content deliverycampaign. Thus, an association between the user and the content deliverycampaign is made. Later, when a content request that is initiated by theuser is received, all the content delivery campaigns that are associatedwith the user may be quickly identified, in order to avoid real-time (oron-the-fly) processing of the targeting criteria. Some of the identifiedcampaigns may be further filtered based on, for example, the campaignbeing deactivated or terminated, the device that the user is operatingbeing of a different type (e.g., desktop) than the type of devicetargeted by the campaign (e.g., mobile device).

A final set of candidate content delivery campaigns is ranked based onone or more criteria, such as predicted click-through rate (which may berelevant only for CPC campaigns), effective cost per impression (whichmay be relevant to CPC, CPM, and CPA campaigns), and/or bid price. Eachcontent delivery campaign may be associated with a bid price thatrepresents how much the corresponding content provider is willing to pay(e.g., content delivery system 120) for having a content item of thecampaign presented to an end-user or selected by an end-user. Differentcontent delivery campaigns may have different bid prices. Generally,content delivery campaigns associated with relatively higher bid priceswill be selected for displaying their respective content items relativeto content items of content delivery campaigns associated withrelatively lower bid prices. Other factors may limit the effect of bidprices, such as objective measures of quality of the content items(e.g., actual click-through rate (CTR) and/or predicted CTR of eachcontent item), budget pacing (which controls how fast a campaign'sbudget is used and, thus, may limit a content item from being displayedat certain times), frequency capping (which limits how often a contentitem is presented to the same person), and a domain of a URL that acontent item might include.

An example of a content item selection event is an advertisementauction, or simply an “ad auction.”

In one embodiment, content delivery exchange 124 conducts one or morecontent item selection events. Thus, content delivery exchange 124 hasaccess to all data associated with making a decision of which contentitem(s) to select, including bid price of each campaign in the final setof content delivery campaigns, an identity of an end-user to which theselected content item(s) will be presented, an indication of whether acontent item from each campaign was presented to the end-user, apredicted CTR of each campaign, a CPC or CPM of each campaign.

In another embodiment, an exchange that is owned and operated by anentity that is different than the entity that operates content deliverysystem 120 conducts one or more content item selection events. In thislatter embodiment, content delivery system 120 sends one or more contentitems to the other exchange, which selects one or more content itemsfrom among multiple content items that the other exchange receives frommultiple sources. In this embodiment, content delivery exchange 124 doesnot necessarily know (a) which content item was selected if the selectedcontent item was from a different source than content delivery system120 or (b) the bid prices of each content item that was part of thecontent item selection event. Thus, the other exchange may provide, tocontent delivery system 120, information regarding one or more bidprices and, optionally, other information associated with the contentitem(s) that was/were selected during a content item selection event,information such as the minimum winning bid or the highest bid of thecontent item that was not selected during the content item selectionevent.

Event Logging

Content delivery system 120 may log one or more types of events, withrespect to content item summaries, across client devices 152-156 (andother client devices not depicted). For example, content delivery system120 determines whether a content item summary that content deliveryexchange 124 delivers is presented at (e.g., displayed by or played backat) a client device. Such an “event” is referred to as an “impression.”As another example, content delivery system 120 determines whether acontent item summary that exchange 124 delivers is selected by a user ofa client device. Such a “user interaction” is referred to as a “click.”Content delivery system 120 stores such data as user interaction data,such as an impression data set and/or a click data set. Thus, contentdelivery system 120 may include a user interaction database 128. Loggingsuch events allows content delivery system 120 to track how welldifferent content items and/or campaigns perform.

For example, content delivery system 120 receives impression data items,each of which is associated with a different instance of an impressionand a particular content item summary. An impression data item mayindicate a particular content item, a date of the impression, a time ofthe impression, a particular publisher or source (e.g., onsite v.offsite), a particular client device that displayed the specific contentitem (e.g., through a client device identifier), and/or a useridentifier of a user that operates the particular client device. Thus,if content delivery system 120 manages delivery of multiple contentitems, then different impression data items may be associated withdifferent content items. One or more of these individual data items maybe encrypted to protect privacy of the end-user.

Similarly, a click data item may indicate a particular content itemsummary, a date of the user selection, a time of the user selection, aparticular publisher or source (e.g., onsite v. offsite), a particularclient device that displayed the specific content item, and/or a useridentifier of a user that operates the particular client device. Ifimpression data items are generated and processed properly, a click dataitem should be associated with an impression data item that correspondsto the click data item. From click data items and impression data itemsassociated with a content item summary, content delivery system 120 maycalculate a CTR for the content item summary.

Content Item Feeds

A content item feed is a set of content items that is presented on ascreen of a client device. A content item feed (or simply “feed”)includes user interface controls for scrolling through the feed. A userinterface control for receiving user input to scroll through a feed isreferred to as a scroll element or “thumb.” Content items within feedmay be scrolled up and down or side to side. comprises. A feed may havea limited number of content items or may be an “infinite” feed where, asthe feed is being scrolled through (whether automatically or in responseto user input), additional content items (that have not yet beenpresented in the feed) are presented.

A content item feed contains multiple types of content items. One typeof content item (referred to herein as the “first type”) is one that hasbeen created by one of content providers 112-116 and that is associatedwith a content delivery campaign having targeting criteria that are usedto identify the user or client device that is presenting the contentitem.

Another type of content item (referred to herein as the “second type”)is content that is generated based on activity of users in an onlinenetwork of the user that is viewing the content item. Examples of such acontent item include a content item identifying an article authored by afriend or connection of the user in the online network, a content itemidentifying an article interacted with (e.g., selected, viewed,commented, liked, shared) by such a friend or connection, a content itemidentifying a change in a status of such a friend, a content itemidentifying news pertaining to an organization (e.g., company, academicinstitution, community organization) with which the user is associatedor affiliated, or of which the user a member (e.g., as specified in theuser's online social network). Such content items originate from contentdelivery system 120 and/or publisher system 130.

Another type of content item (referred to herein as the “third type”) isa content item indicating a type of content in which content deliverysystem 120 (or an affiliated system) predicts the user might beinterested. Examples of types of recommended content include people(i.e., potential friends/connections), jobs, and video courses. Suchcontent items do not originate from content providers 112-116 and arenot part of a content delivery campaign. However, the source of the jobsand the authors/providers of the video courses may be third-partyentities relative to content delivery system 120 and/or publisher system130.

Ranking Content Items in a Feed

The number of content items that may be presented to a user in a contentitem feed may be practically limitless. Thus, to ensure user engagementand interest in the content item feed, content delivery system 120 (orpublisher system 130) ranks the possible content items according to oneor more ranking criteria. Example ranking criteria include actual userselection rate of a content item, predicted user selection rate of eachcontent item, and value to content delivery system 120 or publishersystem 130. The “value” may be a bid value that represents how much acontent provider (e.g., content provider 112) will compensate contentdelivery exchange 120 for presenting the content item or if the userselects the content item. “Value” may correspond to another metric, suchas a value to publisher system 130 if the content item is selected.Different types of content items (e.g., second type versus third type),different content items of the first type, and different sub-types ofcontent items (e.g., job recommendations versus course recommendations)may be associated with different values.

Content Item Blindness

If content items of a particular type are displayed too frequently, thenusers may become “blind” to that type of content item. “Blindness” is aphenomenon where a user or group of users consciously or subconsciouslyignore content items of a particular type when browsing a content itemfeed. Such content items become “invisible” to the user(s). Increasedblindness of certain types of content items may have multiple negativeconsequences, such as decreased user engagement with publisher system130 and a decrease in long term monetization power of content deliverysystem 120.

Based on experiments, a correlation exists between blindness and densityof content items of a particular type. “Density” refers to howfrequently content items of a particular type appear in content itemfeed. 100% density of a particular type means that the entire feedcontains content items of the particular type. Similarly, 10% densitymeans that 10% of the content items in a feed are of the particulartype. Even spacing between content items may be enforced. For example,enforcing even spacing of 33% density of a particular type of contentitem means that every third content item in a feed is of the particulartype.

As density increases, blindness tends to increase. Conversely, asdensity decreases, users can unlearn and increase selection (e.g.,click) propensity to some extent.

Parameters for Placing Content Items of the First Type within a Feed

In an embodiment, content delivery system 120 or publisher system 130ensures that content items of the first type are not presented toofrequently within a single content item feed. Multiple parameters may beused to determine where and how often content items of the first typeappear in a feed. One parameter is “minimum gap” whose value defines aminimum gap between two consecutive content items of the first type. Forexample, a minimum gap of four indicates that there must be at leastfour content items of the second type or third type between two contentitems of the first type. Another parameter is “top slot” whose valuedefines the highest position where content items of the first type canbe shown in a content item feed. For example, if top slot is three, thenthe highest ranked content item of the first type may be placed in thethird slot in the feed, but no higher.

Another parameter is “shadow bid.” The value of shadow bid indicates avalue of user engagement with publisher system 130. Shadow bid is avalue for both content items of the first type (e.g., advertisements)and content items of other types, such as organic content items. In oneapproach, shadow bid is a constant value for all content items,regardless of type.

When determining whether to insert a content item of the first type or acontent item of a second type in a slot of a content item feed, at leasttwo content items are considered: (1) the top ranked content item from afirst set of ordered set of content items of the first type and (2) thetop ranked content item from a second set of ordered set of contentitems of the second type. If there are additional types and they aretreated separately from each other, then there may be one or more othersets of content items of those types. Each slot represents anopportunity to raise revenue and/or increase engagement. While contentitems of the first type result in revenue if displayed or selected,content items of the second type generally do not result in revenue whendisplayed or selected. Those, for content items of the second type,their overall value comes in the form of the shadow bid and theprobability of being selected (or otherwise interacted with).

In contrast, the probability of interacting with (e.g., selecting)content items of the first type may be much lower than the probabilityof interacting with content items of other types. Because shadow bid iscombined with (e.g., multiplied by) the probability of user engagement,the higher the shadow bid, the more likely the overall value of acontent item of a second type will exceed the value of a content item ofthe first type.

If shadow bid is the only one of these three parameters that is defined,then it would be possible that (a) very few or no content items of thefirst type would be presented in a content item feed or (b) the contentitem feed might almost entirely consist of content items of the firsttype. Either scenario is not ideal since the former (a) would result inlittle revenue and the latter (b) might result in user disengagementfrom publisher system 130 altogether.

Modifying Minimum Gap

In an embodiment, a first minimum gap value that is used to determinewhere to place content items in a first feed is modified based onperformance data to generate a second minimum gap value. The performancedata may correspond to one or more measurements of performance. Examplemeasurements of performance include, user selection rate of contentitems of the first type, revenue generated from content items of thefirst type, and user engagement in content from publisher system 130,such as content items of the second and/or third type.

For example, if the user selection rate of content items of the firsttype increases, then the first minimum gap value decreases (or thesecond minimum gap value that is determined is less than the firstminimum gap value). As another example, if the user selection rate ofcontent items of the first type increases a particular amount (e.g., 10%from a previous measurement, 0.9% in absolute terms, or past apre-defined threshold), then the first minimum gap value decreases. Asanother example, if user engagement decreases, then the first minimumgap value increases (or the second minimum gap value that is determinedis greater than the first minimum gap value).

The change in a minimum gap value may be a fixed amount (e.g., +/−1 inminimum gap value) or may be a variable amount (e.g., sometimes +/−1while other times +/−2). If the latter, the variable amount may bedetermined based on the extent to which the performance data changesfrom one time period to another. For example, if user selection ratedecreases by at least X % (e.g., 30%) over the last day, then theminimum gap value increases by N (e.g., 3). As another example, if userengagement on a platform increases by Y amount (e.g., +100K) over threedays, then the minimum gap value decreases by M (e.g., 2).

When the second minimum gap value is determined, the second minimum gapvalue may be used for future content item feeds. Thus, the space betweenconsecutive content items of the first type will be based on the (new)second minimum gap value.

Example Process

FIG. 2 is a flow diagram that depicts an example process 200 foradjusting a minimum gap value for content items of the first type, in anembodiment.

At block 210, a first minimum gap value is stored that dictates howclose two content items of a first type may appear in a content itemfeed that contains content items of multiple types.

At block 220, the first minimum gap value is used to place content itemsin a first set of content item feeds. Different feeds in the first setof content item feeds are associated with different users. Additionallyor alternatively, at least two feeds in the first set of content itemfeeds are presented to the same user (e.g., at different times).

At block 230, for each content item feed in the first set of contentitem feeds, performance data is generated that indicates how wellcontent items of the first type perform in the content item feed. Theperformance data may be an average, median, or other percentile userselection rate.

At block 240, based on the performance data, a second minimum gap valueis generated that can be different than the first minimum gap value. Forexample, if the performance data is above a first threshold, then thesecond minimum gap value is set to be lower than the first minimum gapvalue. Conversely, if the performance data is below a second threshold,then the second minimum gap value is set to be higher than the firstminimum gap value. If the performance data holds at a desired level oris within a certain range of values, then the second minimum gap valuemay be the same as the first minimum gap value.

At block 250, the second minimum gap value is used to place contentitems in a second set of content item feeds. The second set of contentitem feeds may be associated with the same user or set of users as thefirst set of content item feeds.

Controller-Based Framework for Modifying Minimum Gap

In an embodiment, a controller-based framework is used to modify aminimum gap value. An example of a type of controller in such aframework is a proportional-integral-derivative (PID) controller. A PIDcontroller continuously calculates an error value as a differencebetween a target value and a measured (or current) value and applies acorrection based on proportional, integral, and derivative terms. Anexample of accurate and responsive correction to a control function iscruise control on a vehicle. The PID controller restores a current speedto the desired or target speed in an optimal way by controlling thepower output of the vehicle's engine.

Certain parameters of a PID controller are initialized at the beginningof the PID process. In an embodiment, parameters include a current userselection rate (or CTR) (e.g., y₀), a current revenue (e.g., r₀), and acurrent minimum gap value (e.g., a₀=6). Also, a target value (e.g., z)is defined as the current user selection rate multiplied by thesummation of 1 plus a lift value (e.g., 0.05) (e.g., z=y₀*(1+lift)).Also, an error parameter or variable is defined and, optionally,initialized to 0 (e.g., e₀=0).

Once these parameters are initialized, the following process may beperformed continuously (e.g., while t=1 to T do):

-   -   a. determine a current user selection rate and a current revenue        (e.g., observer y_(t), r_(t)))    -   b. determine a current error value based on a difference between        the target value and the current user selection rate (e.g.,        e_(t)=z−y_(t))    -   c. determine a proportional value as a proportional weight        multiplied by the current error value (e.g., P=Kp*e_(t))    -   d. determine an integral value as a proportional weight        multiplied by the current error value (e.g., I=Ki*∫_(τ=1) e_(τ))    -   e. determine a derivative value as a derivative weight        multiplied by the current error value (e.g., D=Kd*de/dt)    -   f. determine a control signal (e.g., u_(t)) that is based on the        proportional value, integral value, and derivative value (e.g.        u_(t)=P+I+D)    -   g. determine a next minimum gap value (e.g., a_(t+1)) based on        the control signal.

There are at least two ways to determine the next minimum gap valuebased on the control signal. Those ways are described in the next twosections below.

Constraint-on-Objective Technique

In an embodiment, a forecast of a user selection rate and of anotherobjective is based on different possible values for the minimum gapvalue. The different possible values may be constrained to an absoluteminimum gap value (e.g., 3) and/or an absolute maximum gap value (e.g.,9). An example of the other objective is revenue. The followingdescription is based on this example objective, although otherembodiments may involve a different objective.

A forecast of a user selection rate given a possible minimum gap valuemay be determined based on a history of user selection rates given thatpossible minimum gap value. The forecast may be calculated using arule-based model or a machine-learned model that is trained based onmultiple training instances, each labeled with a user selection rate andone of the features being a minimum gap value during the timecorresponding to user interaction data that was used to calculate thatuser selection rate.

The forecast of a user selection rate given a possible minimum gap valuecan be learned by a time-series model or a regression model. Fortime-series models, the input is a sequence of user selection ratesordered by time (date), the prediction output is the future (e.g., nextday or next t days) user selection rate(s). The prediction is mainlybased on the pattern (e.g., trend, seasonality) of the user selectionpropensity under a given minimum gap. A regression model takes a list offeatures and assumes the prediction output is a function of the givenlist of features. By fitting the training data (previous observed data),the regression model estimates the function and predicts for future userselection rate. The features can include user profiles (e.g., industry,location), platforms (e.g., mobile or desktop), member behaviors oncontent items of a particular type (e.g., reflected in previous userselection rates), and other online activities on publisher system 130,such as whether the user recently applied to one or more jobs.

Similarly, a forecast of revenue (the other objective in this example)given a possible minimum gap value may be determined based on a historyof revenue given that possible minimum gap value. The forecast may becalculated using a rule-based model or a machine-learned model that istrained based on multiple training instances, each labeled with arevenue amount and one of the features being a minimum gap value thatimmediately preceded that revenue amount. The same type of model andfeatures for forecasting user selection rate may be used to forecastrevenue.

After a forecast of user selection rate is made for a possible minimumgap value (e.g., y_(t+1)(a)), a delta value (e.g., δ) is calculated forthe possible minimum gap value, where the delta value (e.g., δ(a)) isbased on a difference between the forecasted user selection rate forthat possible minimum gap value and a summation of the current userselection rate and the control signal (e.g.,δ(a)=y_(t+1)(a)−(y_(t)+u_(t))).

Once a delta value is calculated for each possible minimum gap value,then the minimum gap value that results in the highest revenue subjectto one or more conditions is returned and used as the next minimum gapvalue (a_(t+1)=argmax_(a)(r_(t+1)) where δ(a)≥0). An example of the oneor more conditions is that the delta value is greater than a particularthreshold (e.g., δ(a)≥0), such as greater than or equal to 0, whichensures that the forecasted user selection rate is equal to or higherthan the desired target. Out of all possible minimum gap values thatsatisfy δ(a)≥0, the one with the highest revenue gain is selected.

This constraint-on-revenue technique assumes that the value in eachaction depends on whether the action can maximize revenue and reach thespecified target.

Heuristic Assumption Technique

The heuristic assumption technique utilizes the observation that lowerdensity of content items of the first type results in lower amount ofanother objective (e.g., revenue). Thus, in an embodiment, the currentminimum gap value is tuned step by step until the target objective(e.g., user selection rate) is achieved. For example:

-   -   a. if the control signal is 0 (e.g., u_(t)=0), then the minimum        gap value remains the same (e.g., a_(t+1)=a_(t))    -   b. if the control signal is greater than 0 (e.g., u_(t)>0), then        the new/updated minimum gap value is set to be the minimum        of (1) the current minimum gap value plus a pre-defined value        (e.g., 1) and (2) an absolute maximum value for the minimum gap        value (e.g., 9) (e.g., a_(t+1)=min(a_(t)+1, 9))    -   c. if the control signal is less than 0 (e.g., u_(t)<0), then        the new/updated minimum gap value is set to be the maximum        of (1) the current minimum gap value minus a pre-defined value        (e.g., 1) and (2) an absolute minimum value for the minimum gap        value (e.g., 3) (e.g., a_(t+1)=max(a_(t)−1, 3))

Segment-Specific Minimum Gap Values

In an embodiment, a minimum gap value is determined for different usersor segments of users. Thus, different content item feeds are associatedwith different minimum gap values.

A segment may be defined based on one or more criteria. For example,users that visit publisher system 130 every day are assigned to a firstsegment, users that visit publisher system 130 at least once per weekbut not daily are assigned to a second segment, users that visitpublisher system 130 at least one per month but not weekly are assignedto a third segment, and users that visit publisher system 130 lessfrequently are assigned to a fourth segment.

As another example, users that have a user selection rate within a firstrange (e.g., greater than 5%) are assigned to a first segment, usersthat have a user selection rate within a second range (e.g., between 3%and 5%) are assigned to a second segment, users that have a userselection rate within a third range (e.g., between 1% and 3%) areassigned to a third segment, and users that have a user selection ratewithin a fourth range (e.g., less than 1%) are assigned to a fourthsegment. Embodiments are not limited to the number of segments or howeach segment is defined. However, is it important to define meaningfuland stable segments. Minimum gap values can be control based on segmentbecause it is assumed that, within one segment, users are very similar.

Offline Workflow

FIG. 3 is a block diagram that depicts an example workflow 300 forupdating minimum gap values using different techniques and for differentsegments, in an embodiment. Workflow 300 may be implemented by contentdelivery system 120, publisher system 130, another computer system (notdepicted in FIG. 1), or any combination thereof.

Each rectangular element in workflow 300 corresponds to data and eachdiamond element in workflow 300 corresponds to a process or a job.

Initialization 304 accepts, as input, model configuration 302 andgenerates, as output, an initial history for each model. Although onlytwo models are depicted in workflow 300, workflow 300 may supportmultiple models/variants at the same time.

Model configuration 302 includes, for each model, model specifications,such as a model identifier, parameters (e.g., Kp, Ki, Kd, etc.), atarget (e.g., for CTR), and a V-function (whether constraint onobjective technique or heuristic assumption technique). V-functionrefers to “value function” and represents how good is a state for anagent to be in. The value function is equal to the expected total rewardfor the controller starting from each state (i.e., a minimum gap in thisscenario).

Per-model history 306 includes history information about a particularmodel and each segment of multiple segments, a target for each segment,one or more past errors (e.g., e_(t)) for each segment (e.g., adifference between a target value and an actual value), and one or morepast control signals (e.g., u_(t)) for each segment. Thus, differentsegments may be associated with different targets. Also, the target maychange from time to time (such as where there is a business need), inwhich case the error (e.g., e_(t)) may be computed based on the newtarget. For example, the initial target may be a 2% lift in currentrevenue. Once it is achieved for a while, the target may be changed to a1% lift in current revenue. Due to the seasonality in the system,different targets may be set in different quarters or other timeperiods. When the target changes, the error term is reset to 0.

Similarly, per-model history 308 includes history information aboutanother model and each segment of multiple segments, a target for eachsegment, one or more past errors (e.g., e_(t)) for each segment, and oneor more past control signals (e.g., u_(t)) for each segment. Thus,per-model history 306 corresponds to a first model and a per-modelhistory 308 corresponds to a second model that is different than thefirst model. For example, the first model may be based on theconstraint-on-objective technique while the second model may be based onthe heuristic assumption technique.

Also, the segment definition for one model may be different than thesegment definition for another model. For example, one model may havethree segments while another model may have four segments. As anotherexample, a segment for one model may be defined by the frequency of useractivities on their respective content item feeds, while for anothermodel, the segment is defined by geographic location of users.

Each per-model history is input to one of per-model controllers 320 and322. Other inputs to per-model controller 320 include output fromforecast model 312, member segmentation data 314, and observe feedback316. Inputs to per-model controller 322 include member segmentation data314 and observe feedback 316.

Forecast model 312 produces a forecast of a user selection rate for asegment given a possible minimum gap value and a forecast of a certainobjective (e.g., revenue) for a segment given a possible minimum gapvalue. Input to forecast model 312 is feedback history 310, whichincludes the past N days of feedback (e.g., a user selection rate andrevenue) per segment and an actual minimum gap value of that segmentduring a previous time period. For example, different time periods(e.g., days) may be different with different actual minimum gap values.

Member segmentation data 314 includes a user/memberidentifier-to-segment mapping that maps user/member identifiers tosegments. Each user/member identifier is mapped to one or more segments.For a given segment definition, one user is mapped to a single segment.However, since there may be multiple models and each model has a segmentdefinition, one user can be mapped to multiple segments.

A user is assigned to a segment based on one or more attributes orcharacteristics of the user. For example, online activity of a user isanalyzed to determine to which segment the user is to be assigned. Asanother example, one or more profiles attributes of a user's profile areconsidered for assigning the user to a segment. A segment assignment maybe based on a combination of online activity and user profileattributes. Multiple controllers/models may be experimented with at thesame time by splitting users into multiple experimental buckets. Forusers in a given experimental bucket, those users will be “controlled”by a single controller/model at a time.

Observe feedback 316 determines current user selection rate for eachsegment and a current objective value (e.g., revenue amount) for eachsegment. Such information may be retrieved from another service orcomponent, not depicted. Output of observe feedback 316 is input toper-model controllers 320 and 322.

In an embodiment, the feedback of interest is not limited to userselection rate and a single objective, such as revenue. Other feedbackthat may be considered include user selection rate to other types ofcontent items (e.g., organic content items), user engaged sessioncounts, length of user engaged sessions, etc. Such feedback may be addedinto the constrained optimization framework. One constrainedoptimization problem is formulated as follows:

-   -   maximize revenue, s.t. user selection rate to content items of        the first type>=target.        If user engaged sessions are also monitored, then the        formulation may change as follows:    -   maximize revenue, s.t. user selection rate to content items of        the first type>=target; user engaged sessions>=threshold        where threshold is the desired value for the user engaged        sessions. There is still one target and the error terms for this        target of which to keep track. The other feedback (user        selection rate and user engaged sessions, in this example) is        used for the constrained problem, not for controlling.

Per-model controllers 320 and 322 pertain to different models. Per-modelcontroller 320 determines, for each segment, an updated minimum gapvalue based on the forecast (for that segment) produced by forecastmodel 312, member segmentation data 314, output from observe feedback316, and per-model history 306. For example, per-model controller 320implements the constraint-on-objective technique. The updated minimumgap value may be the same as or different than the most recent minimumgap value. The updated minimum gap value is used to update per-modelhistory 306.

Per-model controller 320 stores the updated minimum gap value inselection per model 330. Thus, selection per model 330 includes aminimum gap value for each segment associated with the correspondingmodel.

Similarly, per-model controller 322 determines, for each segment, anupdated minimum gap value based on member segmentation data 314, outputfrom observe feedback 316, and per-model history 308. For example,per-model controller 322 implements the heuristic assumption technique.The updated minimum gap value for a segment may be the same as ordifferent than the most recent minimum gap value for that segment. Theupdated minimum gap value is used to update per-model history 308.

Per-model controller 322 stores the updated minimum gap value inselection per model 332. Thus, selection per model 332 includes aminimum gap value for each segment associated with the correspondingmodel.

Union selection 340 unions or combines selection per models 330 and 332and outputs the union to variant combination 350. Variant combination350 accepts the union and a user-variant mapping 352 as input.User-variant mapping 352 maps each individual user to a variant. Avariant is a specific experimental bucket, which contains a set ofuser/member identifiers. A variant is mapped to a specific model.Variant combination 350 generates, as output, a user/member-to-minimumgap value mapping 354 that maps different user/member identifiers tominimum gap values.

This mapping is used to update a minimum gap value attribute for eachuser/member. Later, when a user logs into a system (e.g., publishersystem 130), publisher system 130 looks up attributes of the user,including a minimum gap value, and applies the minimum gap value whenpresenting content items of various types in a content item feed for theuser.

Hardware Overview

According to one embodiment, the techniques described herein areimplemented by one or more special-purpose computing devices. Thespecial-purpose computing devices may be hard-wired to perform thetechniques, or may include digital electronic devices such as one ormore application-specific integrated circuits (ASICs) or fieldprogrammable gate arrays (FPGAs) that are persistently programmed toperform the techniques, or may include one or more general purposehardware processors programmed to perform the techniques pursuant toprogram instructions in firmware, memory, other storage, or acombination. Such special-purpose computing devices may also combinecustom hard-wired logic, ASICs, or FPGAs with custom programming toaccomplish the techniques. The special-purpose computing devices may bedesktop computer systems, portable computer systems, handheld devices,networking devices or any other device that incorporates hard-wiredand/or program logic to implement the techniques.

For example, FIG. 4 is a block diagram that illustrates a computersystem 400 upon which an embodiment of the invention may be implemented.Computer system 400 includes a bus 402 or other communication mechanismfor communicating information, and a hardware processor 404 coupled withbus 402 for processing information. Hardware processor 404 may be, forexample, a general purpose microprocessor.

Computer system 400 also includes a main memory 406, such as a randomaccess memory (RAM) or other dynamic storage device, coupled to bus 402for storing information and instructions to be executed by processor404. Main memory 406 also may be used for storing temporary variables orother intermediate information during execution of instructions to beexecuted by processor 404. Such instructions, when stored innon-transitory storage media accessible to processor 404, rendercomputer system 400 into a special-purpose machine that is customized toperform the operations specified in the instructions.

Computer system 400 further includes a read only memory (ROM) 408 orother static storage device coupled to bus 402 for storing staticinformation and instructions for processor 404. A storage device 410,such as a magnetic disk, optical disk, or solid-state drive is providedand coupled to bus 402 for storing information and instructions.

Computer system 400 may be coupled via bus 402 to a display 412, such asa cathode ray tube (CRT), for displaying information to a computer user.An input device 414, including alphanumeric and other keys, is coupledto bus 402 for communicating information and command selections toprocessor 404. Another type of user input device is cursor control 416,such as a mouse, a trackball, or cursor direction keys for communicatingdirection information and command selections to processor 404 and forcontrolling cursor movement on display 412. This input device typicallyhas two degrees of freedom in two axes, a first axis (e.g., x) and asecond axis (e.g., y), that allows the device to specify positions in aplane.

Computer system 400 may implement the techniques described herein usingcustomized hard-wired logic, one or more ASICs or FPGAs, firmware and/orprogram logic which in combination with the computer system causes orprograms computer system 400 to be a special-purpose machine. Accordingto one embodiment, the techniques herein are performed by computersystem 400 in response to processor 404 executing one or more sequencesof one or more instructions contained in main memory 406. Suchinstructions may be read into main memory 406 from another storagemedium, such as storage device 410. Execution of the sequences ofinstructions contained in main memory 406 causes processor 404 toperform the process steps described herein. In alternative embodiments,hard-wired circuitry may be used in place of or in combination withsoftware instructions.

The term “storage media” as used herein refers to any non-transitorymedia that store data and/or instructions that cause a machine tooperate in a specific fashion. Such storage media may comprisenon-volatile media and/or volatile media. Non-volatile media includes,for example, optical disks, magnetic disks, or solid-state drives, suchas storage device 410. Volatile media includes dynamic memory, such asmain memory 406. Common forms of storage media include, for example, afloppy disk, a flexible disk, hard disk, solid-state drive, magnetictape, or any other magnetic data storage medium, a CD-ROM, any otheroptical data storage medium, any physical medium with patterns of holes,a RAM, a PROM, and EPROM, a FLASH-EPROM, NVRAM, any other memory chip orcartridge.

Storage media is distinct from but may be used in conjunction withtransmission media. Transmission media participates in transferringinformation between storage media. For example, transmission mediaincludes coaxial cables, copper wire and fiber optics, including thewires that comprise bus 402. Transmission media can also take the formof acoustic or light waves, such as those generated during radio-waveand infra-red data communications.

Various forms of media may be involved in carrying one or more sequencesof one or more instructions to processor 404 for execution. For example,the instructions may initially be carried on a magnetic disk orsolid-state drive of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 400 canreceive the data on the telephone line and use an infra-red transmitterto convert the data to an infra-red signal. An infra-red detector canreceive the data carried in the infra-red signal and appropriatecircuitry can place the data on bus 402. Bus 402 carries the data tomain memory 406, from which processor 404 retrieves and executes theinstructions. The instructions received by main memory 406 mayoptionally be stored on storage device 410 either before or afterexecution by processor 404.

Computer system 400 also includes a communication interface 418 coupledto bus 402. Communication interface 418 provides a two-way datacommunication coupling to a network link 420 that is connected to alocal network 422. For example, communication interface 418 may be anintegrated services digital network (ISDN) card, cable modem, satellitemodem, or a modem to provide a data communication connection to acorresponding type of telephone line. As another example, communicationinterface 418 may be a local area network (LAN) card to provide a datacommunication connection to a compatible LAN. Wireless links may also beimplemented. In any such implementation, communication interface 418sends and receives electrical, electromagnetic or optical signals thatcarry digital data streams representing various types of information.

Network link 420 typically provides data communication through one ormore networks to other data devices. For example, network link 420 mayprovide a connection through local network 422 to a host computer 424 orto data equipment operated by an Internet Service Provider (ISP) 426.ISP 426 in turn provides data communication services through the worldwide packet data communication network now commonly referred to as the“Internet” 428. Local network 422 and Internet 428 both use electrical,electromagnetic or optical signals that carry digital data streams. Thesignals through the various networks and the signals on network link 420and through communication interface 418, which carry the digital data toand from computer system 400, are example forms of transmission media.

Computer system 400 can send messages and receive data, includingprogram code, through the network(s), network link 420 and communicationinterface 418. In the Internet example, a server 430 might transmit arequested code for an application program through Internet 428, ISP 426,local network 422 and communication interface 418.

The received code may be executed by processor 404 as it is received,and/or stored in storage device 410, or other non-volatile storage forlater execution.

In the foregoing specification, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense. The sole and exclusive indicator of the scope of the invention,and what is intended by the applicants to be the scope of the invention,is the literal and equivalent scope of the set of claims that issue fromthis application, in the specific form in which such claims issue,including any subsequent correction.

What is claimed is:
 1. A method performed by a content delivery system,the method comprising: storing a first minimum gap value that indicatesa minimum number of slots, in a scrollable content item feed, betweentwo content items that are of a first type and that are from differentcontent providers that are separate from the content delivery system,wherein the scrollable content item feed is presented on a screen of acomputing device of a user and contains content items of a plurality oftypes that includes the first type and a second type that is differentthan the first type, wherein multiple content items in the scrollablecontent item feed are presented concurrently on the screen of thecomputing device; using the first minimum gap value to place, inreal-time, content items in a first plurality of scrollable content itemfeeds; for each scrollable content item feed of the first plurality ofscrollable content item feeds, generating performance data that includesone or more measures of performance of content items of the first typein said each scrollable content item feed; based on the performance dataand the first minimum gap value, generating a second minimum gap valuethat is different than the first minimum gap value; using the secondminimum gap value to place, in real-time, content items in a secondplurality of scrollable content item feeds; wherein the method isperformed by one or more computing devices.
 2. The method of claim 1,wherein the second minimum gap value is associated with a first set ofusers, wherein the second plurality of scrollable content item feeds aredisplayed to users in the first set of users, further comprising: whilethe second minimum gap value is associated with the first set of users,storing a third minimum gap value that is different than the secondminimum gap value and that is associated with a second set of users thatis different than the first set of users.
 3. The method of claim 2,wherein online activity of each user in the first set of users satisfy afirst set of criteria and online activity of each user in the second setof users satisfy a second set of criteria.
 4. The method of claim 3,wherein the online activity is a user selection rate, a number of userselections, a number of visits to a particular website or online portal,or a number of content item feed interactions.
 5. The method of claim 1,further comprising: storing a target user selection rate with respect tocontent items of the first type; determining a current user selectionrate with respect to content items of the first type; determining adifference between the target user selection rate and the current userselection rate; updating the second minimum gap value based on thedifference.
 6. The method of claim 5, wherein the second minimum gapvalue is associated with a first set of users, wherein the secondplurality of scrollable content item feeds are displayed to users in thefirst set of users, further comprising: storing, in association with asecond set of users that is different than the first set of users, asecond target user selection rate with respect to content items of thefirst type; determining a second current user selection rate of thesecond set of users with respect to content items of the first type;determining a second difference between the second target user selectionrate and the second current user selection rate; based on the seconddifference, updating a third minimum gap that is associated with thesecond set of users.
 7. The method of claim 5, further comprising:determining a proportional value based on the difference and aproportional weight; determining an integral value based on an integralof the difference and an integral weight; determining a derivative valuebased on a derivative of the difference and a derivative weight;generating a controller value based on the proportional value, theintegral value, and the derivative value; wherein updating the secondminimum gap value is also based on the controller value.
 8. The methodof claim 7, wherein the difference is a user selection rate difference,further comprising: for each possible minimum gap value in a pluralityof possible minimum gap values: generating, based on said each possibleminimum gap value, a forecasted user selection rate and a forecastedrevenue; calculating a particular difference between the forecasted userselection rate and a summation of the current user selection rate andthe user selection rate difference; identifying a particular minimum gapvalue in the plurality of possible minimum gap values that is associatedwith the highest forecasted revenue given a particular conditionassociated with the particular minimum gap value is satisfied.
 9. Themethod of claim 8, wherein the particular condition is that theparticular difference associated with the particular minimum gap valuemust be greater than a particular value.
 10. The method of claim 7,further comprising: if the controller value is greater than a particularvalue, then establishing a current minimum gap value as a minimum of amaximum gap value or a first summation of the second minimum gap valueand a positive value; if the controller value is not greater than theparticular value, then establishing the current minimum gap value as amaximum of an absolute minimum gap value or a second summation of thesecond minimum gap value and a negative value.
 11. One or more storagemedia storing instructions which, when executed by one or moreprocessors, cause: storing, by a content delivery system, a firstminimum gap value that indicates a minimum number of slots, in ascrollable content item feed, between two content items that are of afirst type and that are from different content providers that areseparate from the content delivery system, wherein the scrollablecontent item feed is presented on a screen of a computing device of auser and contains content items of a plurality of types that includesthe first type and a second type that is different than the first type,wherein multiple content items in the scrollable content item feed arepresented concurrently on the screen of the computing device; using thefirst minimum gap value to place, in real-time, content items in a firstplurality of scrollable content item feeds; for each content item feedof the first plurality of scrollable content item feeds, generatingperformance data that includes one or more measures of performance ofcontent items of the first type in said each content item feed; based onthe performance data and the first minimum gap value, generating asecond minimum gap value that is different than the first minimum gapvalue; using the second minimum gap value to place, in real-time,content items in a second plurality of scrollable content item feeds.12. The one or more storage media of claim 11, wherein the secondminimum gap value is associated with a first set of users, wherein thesecond plurality of scrollable content item feeds are displayed to usersin the first set of users, wherein the instructions, when executed bythe one or more processors, further cause: while the second minimum gapvalue is associated with the first set of users, storing a third minimumgap value that is different than the second minimum gap value and thatis associated with a second set of users that is different than thefirst set of users.
 13. The one or more storage media of claim 12,wherein online activity of each user in the first set of users satisfy afirst set of criteria and online activity of each user in the second setof users satisfy a second set of criteria.
 14. The one or more storagemedia of claim 13, wherein the online activity is a user selection rate,a number of user selections, a number of visits to a particular websiteor online portal, or a number of content item feed interactions.
 15. Theone or more storage media of claim 11, wherein the instructions, whenexecuted by the one or more processors, further cause: storing a targetuser selection rate with respect to content items of the first type;determining a current user selection rate with respect to content itemsof the first type; determining a difference between the target userselection rate and the current user selection rate; updating the secondminimum gap value based on the difference.
 16. The one or more storagemedia of claim 15, wherein the second minimum gap value is associatedwith a first set of users, wherein the second plurality of scrollablecontent item feeds are displayed to users in the first set of users,wherein the instructions, when executed by the one or more processors,further cause: storing, in association with a second set of users thatis different than the first set of users, a second target user selectionrate with respect to content items of the first type; determining asecond current user selection rate of the second set of users withrespect to content items of the first type; determining a seconddifference between the second target user selection rate and the secondcurrent user selection rate; based on the second difference, updating athird minimum gap that is associated with the second set of users. 17.The one or more storage media of claim 15, wherein the instructions,when executed by the one or more processors, further cause: determininga proportional value based on the difference and a proportional weight;determining an integral value based on an integral of the difference andan integral weight; determining a derivative value based on a derivativeof the difference and a derivative weight; generating a controller valuebased on the proportional value, the integral value, and the derivativevalue; wherein updating the second minimum gap value is also based onthe controller value.
 18. The one or more storage media of claim 17,wherein the difference is a user selection rate difference, wherein theinstructions, when executed by the one or more processors, furthercause: for each possible minimum gap value in a plurality of possibleminimum gap values: generating, based on said each possible minimum gapvalue, a forecasted user selection rate and a forecasted revenue;calculating a particular difference between the forecasted userselection rate and a summation of the current user selection rate andthe user selection rate difference; identifying a particular minimum gapvalue in the plurality of possible minimum gap values that is associatedwith the highest forecasted revenue given a particular conditionassociated with the particular minimum gap value is satisfied.
 19. Theone or more storage media of claim 17, wherein the instructions, whenexecuted by the one or more processors, further cause: if the controllervalue is greater than a particular value, then establishing a currentminimum gap value as a minimum of a maximum gap value or a firstsummation of the second minimum gap value and a positive value; if thecontroller value is not greater than the particular value, thenestablishing the current minimum gap value as a maximum of an absoluteminimum gap value or a second summation of the second minimum gap valueand a negative value.
 20. The method of claim 1, wherein the one or moremeasures of performance include one or more of user selection rate ofcontent items of the first type, revenue generated from content items ofthe first type, and user engagement in content of the second type or ofa third type that is different than the first type and the second type.